1. Field of the Invention
This invention relates to thickened cyanoacrylate compositions.
2. Brief Description of Related Technology
Cyanoacrylate compositions are well known as one component reactive adhesives, which are quick bonding and suitable for applications on variety of substrates.
Because cyanoacrylate compositions are inherently of a low viscosity, some applications, such as those where a substrate having large pores is used, are cumbersome. For that reason, thickened cyanoacrylate compositions were developed. Reported thickeners include acrylate resins, such as poly(methyl(meth)acrylate), polymeric alkylcyanoacrylates, cellulose esters, such as cellulose acetate and cellulose butyrate, and polyvinyl ethers, such as polyvinylmethyl ether. See U.S. Pat. No. 3,742,018.
However, traditional cyanoacrylate compositions have been thickened successfully commercially with only a poly(methylmethacrylate) or poly(vinylacetate), which have been used in higher viscosity versions of cyanoacrylate compositions, such as those available commercially under the LOCTITE tradename, bearing for instance the product numbers 406, 416, 424 or 431. In addition, in terms of cyanoacrylate compositions in gel form thixopropic agents such as fumed silica have been used successfully on a commercial scale, such as with those products commercially under the LOCTITE tradename, bearing for instance the product number 454. See U.S. Pat. No. 4,533,422 and Re. 32,889, and U.S. Pat. No. 4,837,260. The thixotropic, fumed-silica-containing cyanoacrylate compositions are described as being in the form of a nonflowable gel which will not substantially move when placed on a substrate. These cyanoacrylate compositions may also contain thickeners, such as for the purpose of preventing the fumed silica from settling in the composition. Disclosed thickeners include poly(meth)acrylates, polycyanoacrylates, and poly(vinyl)acetates.
It is well known to formulate adhesives in the form “stick” compositions. The patent literature on adhesives in “stick” form is extensive and covers a broad range of adhesive types, describing for instance emulsion adhesives, solvent based adhesives, and contact adhesives. In addition, gelling and solidifying additives for the preparation of such stick adhesives report the use of natural polymers and inert fillers. An example of one such adhesive stick is sold under the tradename PRITT STICK by Henkel KGaA. This is an emulsion-based adhesive.
A number of patent documents identify adhesive compositions that have been formulated as soft-solids, and in some cases sticks. For instance, U.S. Pat. No. 5,433,775 discloses an adhesive stick consisting of a water-based preparation of starch derivatives and a soap gel as the shaping gel-forming component. See also U.S. Pat. No. 5,371,131.
U.S. Pat. No. 3,846,363 relates to an adhesive crayon composition containing a sorbitol-benzaldehyde reaction product as an additive. U.S. Pat. No. 4,639,475 discloses an adhesive stick composed of the reaction product of sorbitol and/or xylitol and benzaldehyde as the gel-forming composition together with an adhesive resin which is the reaction product of methyl vinyl ether/maleic acid anhydride copolymers with partially neutralized acid phosphate esters of non-ionic wetting agents of the lower alkylene oxide adduct type. Room temperature dimensionally stable cyanoacrylate compositions have also been prepared with condensation products of aldehydes and ketones with polyols, such as dibenzylidene sorbital. See International Patent Publication Nos. WO 00/32709 and WO 01/91915, and Canadian Patent Application No. CA 2,353,605.
Japanese Patent Document No. 51-103,939 describes a stick-like epoxy adhesive and a stick-like epoxy hardening agent which is used therewith. The sticks in JP '939 patent document seem to be obtained by compounding a gelling agent and/or water and/or organic solvent with a liquid or solution type epoxy adhesive and an epoxy hardening agent.
German Patent Document No. DE 199 57 677 A1 describes a cyanoacrylate adhesive, coating or sealing material, which also contains at least one condensation product of an aldehyde or ketone with a polyol. The adhesive may be in stick form.
U.S. Pat. No. 4,497,916 discloses a continuous liquid phase non-cyanoacrylate adhesive composition to which is added solid wax-like particles dispersed therein. These particles may be chosen from polyethylene glycol materials having 4,000 to 20,000 molecular weight, stearic acid, acid waxes or stearic esters. The compositions disclosed in the '916 patent are formed by heating this combination of materials in slurry form and applying it, while heated, to threads. The composition then cools to obtain a non-mobile coating. This composition requires substantial preparation in order to obtain the composition and apply it on parts. U.S. Pat. No. 3,547,851 discloses anaerobic compositions, which have been rendered non-flowable through the inclusion of various waxes.
U.S. Pat. No. 6,451,927 describes a non-flowable poly(meth)acrylate adhesive composition having a polymeric matrix in sufficient quantity where it is non-flowable at temperatures up to 180° F. (82° C.) while being dispensable at room temperature without the application of heat.
Recently, Henkel Corporation introduced a line of adhesive products in the form of a stick. For instance, LOCTITE QUICK STIK 248, 268, 668, 548, 536 and PST 561 are members of that product line. However, conspicuously absent from this product line is one based on cyanoacrylates. One reason for this is that cyanoacrylates are notoriously sensitive to premature polymerization or destabilization, which is because of the cure profile or physical characteristics of the cyanoacrylate.
Accordingly, it would be desirable to provide a thickening agent for use as a constituent in cyanoacrylates that can be used in a variety of concentrations without adversely affecting the shelf life of the cyanoacrylate while having a dramatic impact on the viscosity, permitting the formulation of cyanoacrylates in a variety of viscosities up to and including a non-flowable form at room temperature.